When Martin Luther King Jr. was murdered, I was 19 years old and fancifully considered myself to be far to the left of him. Notwithstanding that, he felt to me like one of my moral elders and tutors (as he still does). When I was first asked to sign a petition to make his birthday a national holiday, on a Manhattan side street in 1970, I was 21 and signed with pride. When, in 1983, President Ronald Reagan finally signed also, authorizing the bill for the King holiday, I was humbled to think of how far along I was in my 30s and how comparatively little I had to show for it. And last weekend, reading a beautiful reminiscence by King biographer Taylor Branch, I was arrested by the realization that King has now been dead for longer than he was alive, and that it’s been 40 years.